Casey Bralla on 21 Jun 2008 12:43:18 -0700

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[PLUG] Why Virtualize?

I've been thinking about virtualizing on servers.  Although I know that 
virtualized servers are the "next big thing", I can't for the life of me 
figure out the advantage for virtualizing servers, except for a few very 
narrowly specific situations.  

As I've understood it, virtualizing lets you run dozens (hundreds?) of servers 
on the same hardware.  This saves energy because a single fully loaded server 
requires less electricity that dozens of partially loaded servers.  This also 
means you can reduce the number of servers, saving space, physical 
maintenance, etc.  (Cooling costs will only go down in proportion to 
electricity consumption, so not as dramatic a savings there.)

But why not simply run dozens (hundreds?) of server **instances** on the same 
server?   Why add the extra overhead of the virtualization process to the 
hardware?   That has to cut efficiency by at least a few percent.

So what is the advantage of running a complete virtualized server instead of 
multiple server processes?  I can think on only 1:  Clearly assignable 
responsibility for operation.    (If I am responsible for apache on a server, 
and you are responsible for sendmail, I'll try to blame you when I screw up 
and apache stops working.)  Virtualization also is good where someone is 
selling customer-maintained server time in a server farm.  (Again, to isolate 
human responsibility, not to isolate program execution, per se.)

But other than this specific case, what the heck is the advantage?


Casey Bralla
Chief Nerd in Residence
The NerdWorld Organisation
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